Hi Guys, I just copy my post from the other parts of the forum, where is the same discussion, because I think, it is the same problem. The MBA not able to working the 2.4 Ghrtz wifi, they just working fine 5Ghrtz wifi, so maybe you Guys have to try an airport express or an new router which is working on 5 GHrtz.
"Hi Guys!
I just little bit speak english, I hope, you will understand me. I have bought a MBA 2012 MID the last black friday. My issues was absolutly same like Peverbian wife's MBA. All the other OLD thing (PCs, phones etc are working fine in the house, but the new really expensive laptop can not working of course....) I took my MBA back to the Apple Store, they exchanged two parts in this ..... and the problem is stayed with me. (it worked fine in the store, but at my house it does not working ) I was so mad and sad beacuse I dont have a thime for this ( go back again, etc), so I bought the airport express $99 and now it is working. I dont think so it is fair from the apple, because they has to know about the issue, all the forums are full with that and WOW!!!... the newest MBA has the same issue! (https://discussions.apple.com/thread/5100655?start=0&tstart=0)
So, now it is working in my house, but If I go somewhere, I have to pray, because it is not working everywhere.... and I dont want to bring my airport express with myself everywhere, it is nonsense!!!!
I was thinking, I change my MBA for the new MBP. I checked the recycling program. I have bought that half year ago $1700, and now in the the recycling program, the can send me $831 gift card about that Macbook..... Khmm....
So I think, the only solution YET!!! is maybe a new router (which is able to work on 5Ghrz), or an Airport Extreme... :(((((
I hope i could help for Somebody!"